iio: adc: ad7192: Update clock config

iio: adc: ad7192: Update clock config

There are actually 4 configuration modes of clock source for AD719X
devices. Either a crystal can be attached externally between MCLK1 and
MCLK2 pins, or an external CMOS-compatible clock can drive the MCLK2
pin. The other 2 modes make use of the 4.92MHz internal clock.

Undocumented properties adi,int-clock-output-enable and adi,clock-xtal
still supported for backward compatibility, but their use is highly
discouraged. Use cleaner alternative of configuring external clock by
using clock names mclk and xtal.

Functionality of AD7192_CLK_INT_CO will be implemented in complementary
patch by adding clock provider.

Signed-off-by: Alisa-Dariana Roman <alisa.roman@analog.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240717212535.8348-3-alisa.roman@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>